Functional Material Arresting System

Abstract

The present invention relates to a vehicle arresting system comprising an arrester bed 1 of a compressible foam material having a bulk compressive strength and a central longitudinal axis A-A' extending from a front end to an opposite rear end, wherein the arrester bed comprises a set of linear zones having a compressive strength lower than the bulk compressive strength extending parallel to the central longitudinal axis of the bed and / or is inclined at an angle α towards the central longitudinal axis of the arrester bed, where 0°<α<45°.

Description

[Technical field]

[0001] The present invention relates to an engineered material arresting system (EMAS) bed for slowing and steering vehicles / aircraft that cannot stop under their own power. More precisely, the invention relates to an EMAS bed that has a guidance effect on the vehicle that enters the bed. [Background technology]

[0002] A runway overrun is a landing accident with potentially fatal consequences caused by an aircraft failing to stop before reaching the end of the runway. Typical causes of runway overruns are pilot error, bad weather, and / or technical failure of the aircraft.

[0003] An Advanced Material Arresting System (EMAS) is a system installed at the end of a runway to help stop aircraft that are unable to stop before reaching the end of the runway. EMAS design typically involves optimizing the geometry of the bed to provide the best overall fleet performance. Fleet optimization requires compromises, resulting in suboptimal performance for some of the aircraft. Shallow beds and softer materials improve stopping performance for smaller aircraft, but larger aircraft require the opposite characteristics. As a result, there is a great incentive to develop EMAS concepts that can improve the performance of a mixed fleet of large and small aircraft. Since most airports service a wide range of aircraft, EMAS should advantageously be designed to stop aircraft of very different sizes, ranging from as little as 12 metric tons to as much as 450 metric tons. Aircraft may have very different tire sizes, ranging from less than 50 cm in diameter to more than 145 cm in diameter. EMAS are designed specifically for the typical fleet of aircraft served by a particular airport and are tailored to the space available beyond the end of the runway.

[0004] Prior Art EMAS typically consist of a large, shallow bed of absorbent material that engages the aircraft's tires and absorbs the aircraft's kinetic energy to bring the aircraft to a controlled stopping position. Commercially available EMAS use different types of construction, but the primary absorbent material is typically cementitious foam blocks or glass foam aggregate.

[0005] No. 3,967,704 describes a safety device for rapidly arresting the movement of vehicles such as airplanes and automobiles by forming a deceleration bed of crushable material adjacent to the vehicle's track. A foam is formed from an aminoplastic resin composition and placed in the bed adjacent to the vehicle's track where it is cured in situ to provide a compressive strength of 15 to 50 psi (0.10 to 0.34 MPa) and a compressive strength of 0.25 to 10 pounds per cubic foot (4 to 160 kg / m 3 The document describes an exemplary embodiment of a bed having a uniform thickness at a central location and sloping sides to provide a focusing effect for the aircraft using it.

[0006] US 5,885,025 describes a vehicle arresting bed assembled from multiple blocks of porous concrete having a predetermined compressive gradient strength such that the landing gear of the aircraft experiences drag effective to slow various types of aircraft while providing deceleration within safe values. The arresting bed typically includes an entrance region of increasing depth from 9 to 24 inches (23 to 61 cm) formed of blocks having a first compressive gradient strength. A second region, tapering toward the first region and increasing in depth to 30 inches (76 cm), is formed from blocks having a greater compressive gradient strength. Thus, aircraft experience an increase in drag while passing through the bed, providing a stopping capability suitable for a variety of aircraft. A protective hard coat layer of porous concrete, of greater strength than the blocks, overlies the blocks, allowing service personnel to walk on the bed without being damaged. The arresting bed system may be provided in alternative configurations, such as a bed formed from aggregate including pieces of porous concrete with or without interspersed pieces of other compressible material and covered by a hard coat layer. This document further discloses an exemplary embodiment in which the block cell cement of a first row has a lower compressive gradient strength than blocks of subsequent rows in order to increase the longitudinal retardation effect of the aircraft.

[0007] US10,458,073B2 discloses a system and method for stopping an aircraft. In certain embodiments, the system and method may be useful for stopping light aircraft, since light aircraft do not have the weight to penetrate the typically available EMAS systems. The system is generally provided as a structure having a suspension layer of energy absorbing material. The lower part of the system may have a lower strength that is used as a way to suspend the stronger / more energy absorbing upper part of the system.

[0008] The concept of using block foam glass material has been explored by the US Transportation Research Council and documented in ACRP Report29[1]. Glass foam block material was determined to have many desirable EMAS properties, including a nearly ideal compressive stress-strain curve, chemical inertness, low strain rate dependence, environmental durability, and flammability. The report describes a design concept that includes glass foam arranged in prefabricated blocks or assembled on-site at the runway. The block concept includes joints and seams between the blocks, but can be constructed in a built-up approach to provide a continuous surface. Because glass foam is typically manufactured in relatively small block or board shapes, the report envisioned smaller boards being glued together to create larger blocks or constructed in layers to create a monolithic bed.

[0009] ACRP Report 29 also describes a prefabricated block of varying depths in which multiple layers of compressible foam material with different compressive strengths are glued together with the softer layers located near the surface of the bed and the harder layers located near the bottom. This concept was intended to help improve arrester bed performance when there is a mixed aircraft fleet. Lighter aircraft will primarily engage with the softer layers of compressible foam near the surface, while heavier aircraft will penetrate deeper and engage with the harder layers of foam near the bottom. The report describes modeling and simulation results that showed improved mixed fleet performance compared to an EMAS with a single material strength throughout the thickness.

[0010] US2019 / 084693 discloses a vehicle arresting system comprising a base layer comprising crushable aggregate and a cover layer comprising a cementitious material having an oven-dry density of 100 lb / ft3 or less. The system may also include an arrester bed and a plurality of anchors. Each anchor comprises a support rod coupled to an associated puck, each support rod being fixed to a foundation supporting the arrester bed, and each puck being embedded in a cover layer slab of the arrester bed. Further, each support rod is coupled to its associated puck via a shear link breakable at a predetermined load. A method of stopping a vehicle includes depositing a base layer comprising aggregate in an area where the vehicle is to be stopped, and depositing a cover layer comprising a cementitious material having an oven-dry density of 100 lb / ft3 or less on the base layer.

[0011] US2015 / 247298 discloses macro-patterned materials and methods of their use in connection with vehicle arresting systems. Certain embodiments provide 3D folded materials, honeycombs, lattice structures, and other periodic cellular material structures that can be used to stop vehicles. The materials can be engineered to have properties that allow them to reliably fracture in a predictable manner under pressure from the vehicle. The materials may be formed into various shapes and combined in various ways to provide the desired properties.

[0012] The variable depth concept was first proposed in ACRP Report 29 as consisting of multiple layers or tiers of compressible foam bonded together to complete the thickness of the EMAS bed. The bottom layer of the block has the highest density and crush strength, while the top layer has the lowest density and crush strength. The variable depth nature of the bed provides improved mixed fleet stopping performance by allowing lighter aircraft to engage the softer upper layers, while heavier aircraft penetrate deeper and engage the harder underlayer of material.

[0013] An aircraft overrun is an emergency situation in which one or more things go wrong. When an overrun occurs, the aircraft often does not exit along the runway centerline, but instead may be offset to the left or right. The aircraft may also not travel in a direction parallel to the runway, but instead may turn along the diagonal of the movement. Additionally, typical designs of runways include shallow side slopes to facilitate drainage, which may increase turning behavior in some situations. When an aircraft turns diagonally, it may end up taking a shorter path through the EMAS arrester bed. This results in an early exit along the side edge of the bed, thereby shortening the length of travel through the bed and reducing the protection that the EMAS is designed to provide. EMAS does not currently have design features to control the path of aircraft movement, and innovations that can provide a centering effect are desirable.

[0014] Object of the invention The primary objective of the present invention is to provide an Advanced Material Arresting System (EMAS) bed for slowing and steering vehicles / aircraft that cannot stop under their own power. Summary of the Invention

[0015] The present invention is based on the recognition that linear zones of relatively low or otherwise higher compressive strength material in the EMAS bed can be utilized to provide a directional load to the EMAS bed against the wheels of an overrunning vehicle / aircraft to help steer the vehicle / aircraft as it moves longitudinally through the EMAS bed.

[0016] Accordingly, in a first aspect, the present invention relates to a vehicle arresting system including an arrester bed of a compressible foam material having a bulk compressive strength and a central longitudinal axis extending from a forward end to an opposite aft end, The arrester bed further comprises a plurality of linear zones of compressible foam material having a compressive strength lower than the bulk compressive strength of the compressible foam material, and each of the plurality of linear zones a) extends parallel to the longitudinal central axis of the bed, or b) is inclined at an angle α of 0° < α ≤ 45° towards the longitudinal central axis of the arrester bed, such that the plurality of linear zones form an inverted V-pattern in the direction from the front end to the rear end of the arrester bed as seen from above, or c) is a combination of a) and b).

[0017] As used herein, the term "longitudinal direction" refers to the direction in which a vehicle / aircraft entering the arrester bed is expected to move across the arrester bed. As used herein, the term "front end" is the side where a vehicle / aircraft is expected to enter the arrester bed / EMAS, and the "rear side" is the opposite side of the front end. The arrester bed may, in some embodiments, be shaped as a longitudinally rectangular bed (as seen from above), i.e., having a relatively short width compared to its diagonal length.

[0018] As used herein, the term "arrester bed" refers to a bed of compressible foam material placed on the ground or pushed into the ground, for example, a washbasin filled with compressible foam material. The arrester bed is, in some embodiments, placed at the end of a runway, but may be placed / applied anywhere where a vehicle / aircraft may be expected to (unintentionally) require external assistance to effect a controlled stop. However, in the following, the arrester bed is described in relation to the need to avoid overruns at airports and for aircraft, but the arrester bed according to the present invention is not limited to airports and aircraft, and is applied to absorb kinetic energy and can stop any wheeled vehicle moving across the arrester bed at any position where such functionality is desired.

[0019] The present invention according to the first aspect is not bound to any particular design, size or location, but encompasses any size and design of arrester bed known or conceivable to a person skilled in the art. Moreover, the present invention does not depend on how the arrester bed is made and assembled. Any known conceivable method of forming a bed of compressible foam material at the location where the arrester bed is to be placed is included in the present invention as long as the arrester bed comprises a set of linear zones of relatively low compressive strength that are a) arranged parallel to the longitudinal central axis of the bed, or b) inclined at an angle α of 0°<α≦45° toward the longitudinal central axis of the bed forming an inverted V-pattern with respect to the direction from the front end to the rear end of the arrester bed, or a combination of a) and b). In some embodiments, the set of linear zones of relatively low compressive strength may be angled at an angle α, 0°<α≦40°, preferably 1°<α≦35°, more preferably 2°≦α≦30°, more preferably 3°≦α≦25°, more preferably 4°≦α≦20°, more preferably 5°≦α≦15°, most preferably 5°≦α≦10°, forming an inverted V-pattern with respect to the direction from the front end to the rear end of the arrester bed toward the longitudinal central axis of the bed. It is clear from the context that the angle α toward the longitudinal central axis of the arrester bed is an angle formed in the horizontal plane such that the inclination of the linear zones causes a lateral force on a vertically oriented wheel moving longitudinally through the arrester bed.

[0020] The compressible foam material of the arrester bed has a mechanical strength adjusted so that the arrester bed cannot advance the wheels of a vehicle / aircraft that enters the arrester bed, but sinks a distance within the compressible foam material so that the compressible foam material absorbs kinetic energy from the vehicle / aircraft and forces the vehicle / aircraft to a stop, as shown in the photograph of Figure 1. Arrester beds are also referred to in the literature as "functional material arresting systems (EMAS)". These terms are used interchangeably herein.

[0021] The term "compressible foam material" as used herein encompasses any material known to one skilled in the art to be suitable as a deformable / foldable material that engages the oncoming wheels of a vehicle / aircraft and absorbs kinetic energy from the vehicle / aircraft to bring the vehicle / aircraft to a controlled stop. Examples of suitable materials include, but are not limited to, cellular cement, cellular cement-based materials, foamed cement, polymer foam, honeycomb, metal honeycomb, vermiculite, perlite, ceramic foam, foam glass, and other isotropic or anisotropic compressible / deformable materials, or combinations thereof.

[0022] When a compressible foam material is subjected to a stress load, the foam material reaches a certain plateau value, σ, at which the foam material begins to fracture / compress. u , the stress load is maintained until the foam material is gradually compressed during the plateau stress until all or nearly all of the voids in the foam microstructure collapse. At this point, the material has significantly stiffened and further compression requires dramatically higher stress / compression forces. A typical compressive stress-strain curve for a compressible foam material is shown in Figure 2. The degree of compression at the end of the plateau is determined by the maximum compressive strain of the material, ε max , and is important in determining the overall energy absorption potential of a compressible foam material since energy absorption is related to the area under the stress-strain curve. Larger maximum compressive strain values ​​correspond to a longer plateau region in the load curve and higher energy absorption. As used herein, the term "compressive strength" refers to the plateau value, σ, as determined by ASTM CI165-07(2017), unless otherwise specified. u , refers to.

[0023] The compressive strength of the compressible foam material that provides an effective but controlled stopping action on the vehicle / aircraft depends on the expected tire pressure that is pressed against the surface of the arrester bed by the wheels of the vehicle / aircraft entering the arrester bed. Since the mass of the vehicle / aircraft can vary widely, the range of compressive strengths that provide an effective stopping action also varies widely. It is necessary to adapt the compressive strength of the compressible foam material of the arrester bed depending on the vehicle / aircraft that is intended to be stopped by it. The determination of the required compressive strength is within the ordinary skill of the person skilled in the art and may be performed by experimental material testing and / or numerical modeling, as described in ACRP Report 29 [1] (see, for example, Chapters 8 and 9). In practice, for vehicle arresting system applications at passenger airfields, the compressible foam material may advantageously have a compressive strength in the range of 6.9 to 689.8 kPa (1 to 100 psi), preferably 68.9 to 620.5 kPa (10 to 90 psi), more preferably 137.9 to 551.8 kPa (20 to 80 psi), more preferably 206.8 to 482.6 kPa (30 to 70 psi), and most preferably 275.8 to 413.7 kPa (40 to 60 psi).

[0024] The arrester bed may, in some embodiments, have a depth variation in compressive strength, where the compressive strength increases as the depth of the bed increases. This provides the arrester bed with improved performance in the case of a mix of vehicles / aircraft, as the wheels of lighter vehicles only engage the softer upper layers, while the wheels of heavier vehicles / aircraft engage deeper into the arrester bed, as shown diagrammatically in Figures 3a) and 3b). In the arrester bed shown in Figures 3a) and 3b), the depth variation is obtained by providing the arrester bed with a layered structure of multiple layers of compressible foam material having a higher compressive strength for each successive layer of compressible foam material up to the bottom layer of the arrester bed.

[0025] The term "set of linear stripes / zones of relatively low energy absorption" as used herein encompasses any possible way of providing the arrester bed with a straight, relatively narrow zone in the arrester bed in which the energy absorbing material has a lower compressive strength, and / or any other way of obtaining a relatively low braking effect for a wheel passing along such linear stripes / zones compared to passing through the bulk material of the arrester bed. The set of linear stripes / zones of relatively low energy absorption can be obtained in any known or conceivable way, including, for example, applying a compressible foam material having a relatively low compressive strength to each linear stripe / zone, applying a compressible foam material having a higher porosity than the bulk compressible foam material to each linear stripe / zone, forming through holes in the material of each linear stripe / zone, forming linear channels / recesses / trenches in the upper surface a distance down into the arrester bed that extend partially or completely through the depth of the arrester bed, etc.

[0026] Since each straight zone is "surrounded" on both sides by bulk compressible foam material of relatively high compressive strength, the wheels of a vehicle / aircraft entering a straight zone find it easier to move along the straight zone than to move into the bulk part of the arrester bed. When trying to move out of the soft zone and into the relatively hard compressible foam material on the side of the soft zone, there is a lateral force that pushes the wheels back into the soft zone. A set of linear stripes / zones oriented as in option a) of the first aspect of the invention provides an arrester bed according to the invention with a course correction effect that tries to guide the path of movement of the wheels of a vehicle entering the arrester bed to move in a straight line parallel to the longitudinal central axis of the arrester bed. This effect is advantageous by contributing to align the vehicle path in the longitudinal direction when the aircraft / vehicle enters the arrester bed in a transverse direction, thus ensuring a maximum passing length and therefore a maximum braking effect. Linear stripes / zones oriented as in option b) of the first aspect of the present invention and shaped into an inverted V pattern exhibit the above-mentioned orientation effect, but also a centering effect which helps vehicles pass through the arrester bed in a parallel manner and along the longitudinal central axis of the arrester bed.

[0027] The arrester bed may, in some embodiments, be comprised of prefabricated blocks of compressible foam material that are assembled and glued together on-site to form the arrester bed. The adhesion of the blocks to each other may be obtained in any known or conceivable manner, for example, by gluing, caulking, adhesive tape, etc.

[0028] In some embodiments, the prefabricated blocks are shaped as a rectangular parallelepiped with a rectangular base of length l and width w (w≠l), and height h (h may be the same or different than width w and / or length l). In some embodiments, the prefabricated blocks are shaped as a rectangular parallelepiped with a square base of length l, width w (w=l), and height h (h may be the same or different than width w and length l).

[0029] In some embodiments, the arrester bed may be assembled by blocks of various sizes and / or heights. For example, the peripheral blocks may in some embodiments be reduced in height compared to the blocks in the middle part of the arrester bed, tapering the edges of the arrester bed. In other embodiments, the arrester bed may be given a soft entry by applying successive rows of blocks of increasing height from the front end and increasing distance into the arrester bed, and the bed from the arrester bed may have a constant thickness (height).

[0030] In some embodiments, the arrester bed may be provided with a cover layer over the compressible energy absorbing material to protect against the environment, jet blast, etc. The present invention may apply any known conceivable cover layer known to those skilled in the art as suitable for an arrester bed made of foamed / compressible energy absorbing material. Examples of suitable cover layers include a thin plastic top, a cement board top, a polymeric coating or sealant, a paint, or a combination thereof.

[0031] In some embodiments, the arrester bed may be assembled from blocks having equal widths from front to rear such that longitudinally linear vertical interfaces between the blocks are formed that extend through the arrester bed. By applying no adhesive or a relatively weak adhesive to these interfaces, the longitudinally oriented interfaces function as a set of linear stripes / zones of relatively low energy absorption according to the first aspect of the invention.

[0032] In some embodiments, each block may be made of several smaller blocks 7 glued together in a stack, for example by gluing. This gives the prefabricated block a layered, layered structure. This method of assembling the blocks into an arrester bed is sometimes called the block method. An example of such an assembly for making an EMAS is shown diagrammatically in FIG. 4a). The figure shows a schematic illustration of an arrester bed 1 consisting of several rows 2, each row consisting of several blocks of compressible energy absorbing material arranged side by side. As can be seen from the detailed enlargement, each block 10 of the bulk part of the arrester bed is made up of several, here four, layers of smaller blocks 7 stacked and glued on top of each other. In this embodiment, the tapering at the front end may be obtained simply by applying a smaller number of smaller blocks in the stack for the first row of the arrester bed. The rows 2 are sealed and glued together along their sides 6 by gluing or other suitable methods. The sides of the block perpendicular to side 6, i.e. the sides parallel to the longitudinal axis of the arrester bed, may also be sealed and glued in the same way, or may not be glued / attached to each other, or may only be relatively lightly glued to have longitudinally oriented sides that act as a set of linear zones according to the first aspect of the invention. The embodiment shown in Figures 4a) and 4b) comprises a covering layer 5.

[0033] In some embodiments, the block may have a layered, tiered structure, where each layer is made of smaller blocks 8, and where each layer is offset with respect to the layer below it, such that the smaller blocks 8 form a brick pattern as shown in FIG. 4b). That is, the prefabricated block comprises a vertical stack of multiple layered layers 9 glued together, where each layered layer 9 is made of a second multiple smaller blocks 8 arranged in a single horizontal plane, and the smaller blocks 8 of the layered layer 9 are offset from the lower layer to the upper layer with respect to the multiple smaller blocks 8 of the layered layer 9 below and / or above it, such that the smaller blocks 8 of the prefabricated block 10 form a brick pattern. Such a structure results in an arrester bed with more monolithic mechanical properties.

[0034] In embodiments having a hierarchical layered structure, the variation in compressive strength with depth can be obtained by simply gluing together smaller blocks 7, 8 having progressively stronger compressive strengths at lower depths, such that the bottom layer has the highest compressive strength and the top layer has the weakest strength, with each successive layer having a weaker compressive strength than the smaller block below it. An example of such an embodiment is shown in Figures 3a) and 3b).

[0035] In some embodiments, the block with depth variation may have inclined layered layers oriented toward the centerline of the arrester bed. That is, by having the layered layers 9 of the prefabricated block 10 inclined so that the layered layers 9 are substantially parallel (i.e. horizontal) to the longitudinal central axis of the arrester bed and inclined so that they slope laterally downward toward the longitudinal central axis of the arrester bed, the layered layers are inclined so that they slope downward toward the centerline. Figure 5a) is a perspective view from the side and top of a single block 10 having six layers 9 of compressible energy absorbing material with gradually weaker compressive strength toward the top. As can be seen in the figure, each layered layer is somewhat inclined toward the centerline, shown as staple lines marked A and A'. Figure 5b) illustrates the same block as Figure 5a), but now viewed from the side of the front surface. A wheel 12 entering the block 10 and travelling longitudinally comes into contact with a relatively large amount of weakly compressible energy absorbing material on its right side (relative to the direction of travel) and is therefore subjected to a lateral force towards the centreline, as shown by the black arrow in the figure.

[0036] An exemplary embodiment of an arrester bed assembled by blocks with layered layers of varying depth and inclination is shown in FIG. 6. In this exemplary embodiment, the arrester bed 1 comprises eight blocks with layered layers of varying depth and inclination in each row (lateral direction), namely four blocks 10 on the left side of the centerline A-A' and four blocks 13 on the right side. The layer inclination of the blocks 10 on the left side of the centerline causes the layered layers to be inclined downwards towards its right side, and the layer inclination of the blocks 13 on the right side of the centerline causes the layered layers to be inclined downwards towards its left side. As shown in this example, an aircraft approaching the arrester bed off-line, for example, on the left side of the arrester bed, experiences a lateral force that tries to guide the aircraft to be aligned on the centerline. This effect is in addition to the orientation effect of the set of linear stripes / zones with a compressive strength lower than the bulk compressive strength according to the present invention.

[0037] Producing compressible energy absorbing materials at multiple compressive strengths is more expensive and complicated than producing a single strength material. Thus, in some embodiments, the variation in depth of the layers / tiers of the block is obtained by using a single strength compressible energy absorbing material, and can form linear through voids, channels, or holes in the layers such that the percentage of voids in each successive layer decreases toward the bottom of the block. The upper layers produce a softer material response under vehicle / aircraft tire load than the solid compressible energy absorbing material, thereby acting similarly to a lower density compressible energy absorbing material with a lower compressive strength. The lower tiers produce a stiffer material response under aircraft tire load, and in the limit, the strength approaches that of the solid compressible energy absorbing material. The bottom layer can be a continuous compressible energy absorbing material with no voids at all.

[0038] In an exemplary embodiment, the one or second plurality of smaller blocks 7, 8 in the top layer 9 of the layered prefabricated block 10 has a first compressive strength, the one or second plurality of smaller blocks 7, 8 in the first layered layer 9 below the top layer has a second compressive strength, the one or second plurality of smaller blocks 7, 8 in the second layered layer 9 below the top layer has a third compressive strength, and so on down to the bottom layer 9, where the first compressive strength<second compressive strength<third compressive strength, and so on down to the bottom layer 9.

[0039] The degree of variation in the proportion of void space within a layer can be achieved by forming larger and / or more numerous linear through voids, channels or holes within the layer. Linear through voids, channels or holes in a layer can be achieved by milling, drilling or any other known conceivable method suitable for locally removing material from a compressible / foamed material. Alternatively, linear through voids can be achieved by assembling each layer of blocks from relatively narrow strips of compressible / foamed material bonded together with void spaces / gaps between them.

[0040] An exemplary embodiment of a block made of strips glued together to form a layered structure with depth variation of compressive strength is shown in FIG. 7a). The figure shows a view of one block 20 from the side, so that the through voids 22 of the layers 21 are visible. The upper layer, which is the layer immediately below the covering layer 23, is composed of relatively narrow strips 24 with relatively wide voids / gaps 22, and each successive layer 21 up to the block has progressively wider strips 24 and narrower voids / gaps 22, up to the lower layer, which is solid. In the exemplary embodiment shown in FIG. 7b), the layered structure with depth variation of compressive strength is obtained by straight through channels 32 with a cross-sectional area that decreases for each successive layer 31 deeper in the block 30. The embodiment shown in the figure has a covering layer 33. Similarly, in the exemplary embodiment shown in FIG. 7c), the layered structure with depth variation of compressive strength is obtained by straight through holes 42 drilled from the block 40. In this embodiment, the increased percentage of void space is obtained by varying both the diameter and the number of pores in the continuous layer 41. The embodiment shown in the figures has a cover layer 43.

[0041] In some embodiments, the linear through voids, channels or holes in the layers of the block may advantageously be aligned parallel to the central longitudinal axis or angled at an angle α (0°<α≦45°) towards the central longitudinal axis of the arrester bed, or a combination of both, so that they function as linear stripes / zones according to the first aspect of the invention.

[0042] The linear through voids, channels or holes aligned parallel to the longitudinal central axis provide the arrester bed with a course correction effect that guides the path of travel of the wheels of a vehicle entering the arrester bed to travel in a straight line parallel to the longitudinal central axis of the arrester bed. An exemplary embodiment of an arrester bed having linear through voids, channels or holes aligned parallel to the longitudinal central axis is illustrated diagrammatically in FIG. 8. The figure is a top view and illustrates an arrester bed consisting of 14 rows and 12 blocks. As can be seen from the enlarged view in the box with the staple lines, each block 10 (one single block is marked with a staple circle) has a set of linear through voids aligned parallel to the longitudinal central axis of the arrester bed, and the linear through voids in a block are aligned with the linear through voids in blocks at similar positions in successive rows, and they form a continuous void that runs through the entire arrester bed. The sides of the block 10 are marked with solid lines 14, while the straight through gaps are marked on the drawing with staples 13.

[0043] Similarly, linear through voids, channels or holes inclined at an angle α (0°<α≦45°) to the longitudinal central axis of the arrester bed provide a centering effect to the arrester bed that helps the vehicle / aircraft pass through the arrester bed parallel to and along the longitudinal central axis of the arrester bed. In FIG. 9, an exemplary embodiment of an arrester bed having linear through voids, channels or holes angled toward the longitudinal central axis forming an inverted V-shape is illustrated diagrammatically. The figure is a top view and illustrates an arrester bed consisting of 14 rows and 12 blocks. As can be seen from the figure, the linear through voids 15 are angled toward the longitudinal central axis at an angle α on both sides of the central axis, such that each "pair" of linear through voids forms an inverted V-shape. The sides of the blocks 10 are marked with solid lines 14, while the linear through voids are marked on the figure with staples 15. [Brief description of the drawings]

[0044] [Figure 1] Figure 1 is reproduced from Wikipedia https: / / en.wikipedia.org / wiki / Engineered_materials_arrestor_system showing a photograph of an aircraft wheel entering the EMAS bed and being arrested. [Diagram 2] FIG. 2 shows a typical compressive stress-strain curve for a compressible foam material. [Figure 3a)] FIG. 3a) is a schematic diagram illustrating the penetration depth of a heavy wheel (FIG. 3a) penetrating an arrester bed having a layered structure of multiple layers of compressible foam material, with the upper layers having a lower compressive strength and the lower layers of compressible foam material having a higher compressive strength. [Figure 3b)] FIG. 3b) A schematic diagram illustrating the penetration depth of a light wheel (FIG. 3b)) entering an arrester bed having a layered structure of multiple layers of compressible foam material, where the upper layers have a lower compressive strength and the lower layers have a higher compressive strength of the compressible foam material. [Figure 4a)] FIG. 4a is a diagram illustrating a schematic diagram of an exemplary embodiment of a block type arrester bed. [Figure 4b] FIG. 4b is a diagram illustrating a schematic diagram of an exemplary embodiment of a monolith type arrester bed. [Figure 5a)] FIG. 5a) is a diagram illustrating a block with depth variation and tilt according to an exemplary embodiment of the present invention. [Figure 5b] FIG. 5b) is a diagram illustrating a block with depth variation and tilt according to an exemplary embodiment of the present invention. [Figure 6] FIG. 6 is a diagram illustrating an arrester bed assembled from the blocks shown in FIGS. 5a) and 5b). [Figure 7a)]FIG. 7a) is a schematic diagram illustrating an exemplary embodiment of a block having a layered structure with depth variation of compressive strength and through voids according to the present invention, where an embodiment is shown in FIG. 7a) in which the layers with through voids are made by strips glued together at a distance. [Figure 7b] FIG. 7b) is a schematic diagram illustrating an exemplary embodiment of a block having a layered structure with depth-wise variation in compressive strength and through voids according to the present invention, where an embodiment is shown in FIG. 7b) in which the layers with through voids are created by forming channels of decreasing cross-sectional area for each successive layer deeper within the block. [Figure 7c)] FIG. 7c) is a schematic diagram illustrating an exemplary embodiment of a block having a layered structure with depth variation in compressive strength and through voids according to the present invention, showing an embodiment in which straight and through holes are drilled from the block. [Figure 8] FIG. 8 is a top view of an exemplary embodiment of an arrester bed according to the invention having straight through gaps running parallel to the central longitudinal axis of the bed. [Figure 9] FIG. 9 is a top view of an exemplary embodiment of an arrester bed according to the present invention having angled linear through-gaps forming an inverted V-shape. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] The invention is explained in further detail by an exemplary embodiment of an arrester bed intended to stop aircraft and having a depth variation of compressive strength obtained by layers with different compressive strengths.

[0046] Barsotti et al. [1] (see Chapter 12) and Barsotti [2] investigated and found that the optimum change in arrestor bed depth intended for a mixed fleet of aircraft was an increase in compressive strength of 4.3 kPa per cm (1.6 psi per inch) of depth into the arrestor bed, assuming an arrestor bed depth of 76.2 cm (30 in).

[0047] An exemplary embodiment of the arrester bed consisted of 1058 prefabricated blocks of foam glass, each 2.13 m long and 2.13 m wide, and 76 cm high. The blocks were assembled into 23 linear columns and 46 linear rows, resulting in an arrester bed with a width of 49 m and a length of 98 m. That is, the arrester bed covers a surface area equivalent to a small football field.

[0048] Each prefabricated block of this exemplary embodiment of the arrester bed is composed of six layers made of foam glass with a single compressive strength of 358.5 kPa (52 psi), but the variation in depth of the layers is obtained by the varying porosity of the linear voids in the layers. The voids in the layers effectively reduce the average presented area of ​​the material during compression, which reduces the effective compressive strength of the layered cross section.

[0049] In general, the approximate compressive strength of a layer of voided crushable foam is given by the effective compressive strength, σe:

number

[0050] The linear voids in the tiers are formed in this exemplary embodiment by holes drilled through the tiers as shown in Figure 7c), but may alternatively be created by milling grooves as seen in Figure 7b), or by having the tiers constructed of foam glass strips with gaps between them as shown in Figure 7a).As mentioned above, these linear holes drilled in the tiers achieve the function of linear zones with a compressive strength lower than the bulk compressive strength if they are formed to extend parallel to the longitudinal central axis of the arrester bed.

[0051] Since each layer in a 30 inch high bed has a height / thickness of 5 inches (12.7 cm), adjusting the number and / or diameter of holes drilled in each layer to give porosity of 77% for the first (top) layer, 62% for the second layer, 46% for the third layer, 31% for the fourth layer, 15% for the fifth layer, and 0% for the sixth (bottom) layer results in an effective compressive strength σ for each successive layer corresponding to 1.6 psi / inch (4.3 kPa / cm), as given by Equation (1) and summarized in Table 1. e A step-like change in depth is obtained. [Table 1]

[0052] References 1. Matt Barsotti et al. (2009), “ACRP Report 29: Developing Improved Civil Aircraft Arresting Systems” US Transportation Research Board, DOI:10.17226 / 14340 2.M. Barsotti, "Optimization of a Passive Aircraft Arrestor with a Depth-Varying Crushable Material Using a Smoothed Particle Hydrodynamics (SPH) Model," UMI / Proquest LLC, Ann Arbor, 2008.

Claims

1. 1. A vehicle arresting system comprising an arrester bed of a compressible foam material having a bulk compressive strength and a central longitudinal axis extending from a forward end to an opposite aft end, the arrester bed comprising: The arrester bed further comprises a plurality of linear zones of the compressible foam material having a compressive strength lower than a bulk compressive strength of the compressible foam material, each of the linear zones comprising: a) extending parallel to the central longitudinal axis of the bed; or b) inclined at an angle α toward the longitudinal central axis of the arrester bed, 0°<α≦45°, the linear zones forming an inverted V-pattern with respect to the front-to-rear direction of the arrester bed when viewed from above; or c) A vehicle arresting system characterized by a combination of a) and b).

2. 2. The vehicle arresting system of claim 1, wherein the set of linear zones of relatively low compressive strength are angled at an angle α, where 0°<α≦40°.

3. 3. The vehicle arresting system of claim 1 or 2, wherein the compressible foam material is a material selected from cellular cement, cellular cement material, foamed cement, polymer foam, honeycomb, metal honeycomb, vermiculite, perlite, ceramic, foam glass, and other isotropic or anisotropic compressible / deformable materials, or combinations thereof.

4. 3. The vehicle arresting system of claim 1 or 2, wherein the compressible foam material has a compressive strength in the range of 6.9 to 689.8 kPa.

5. 3. The vehicle arresting system of claim 1 or 2, wherein the linear stripes / zones of relatively low energy absorption are one of a compressible foam material having a relatively low compressive strength, a compressible foam material having a higher porosity than bulk compressible foam material, perforations in the compressible foam material, linear channels / recesses / trenches in an upper surface, and a distance into the arrester bed that extends partially or completely through a depth of the arrester bed.

6. 3. The vehicle arresting system of claim 1, wherein the arrester bed has a depth variation in compressive strength that increases with increasing bed depth, obtained by providing the arrester bed with a layered structure of multiple layers of compressible foam material having a higher compressive strength for each successive layer of compressible foam material up to a bottom layer of the arrester bed.

7. the arrester bed is made of prefabricated blocks of the compressible foam material, the prefabricated blocks being assembled and glued together by gluing, caulking or adhesive tape, the prefabricated blocks being a rectangular parallelepiped having a rectangular base of length l and width w, w≠l and height h; or 3. A vehicle arresting system as claimed in claim 1 or 2, which is shaped as either a rectangular parallelepiped having a square base of length l and width w, where w=l, and height h.

8. The assembly block (10) is a vertical stack of layered layers (9) bonded together, each layer (9) consisting of one smaller block (7), or 8. The vehicle arresting system of claim 7, comprising a vertical stack of a plurality of layered layers (9) bonded together, each layered layer (9) consisting of a second plurality of smaller blocks (8) arranged in a single horizontal plane, the smaller blocks (8) of a layered layer (9) being offset from lower layer to upper layer relative to the plurality of smaller blocks (8) of the layered layer (9) below and / or above it, such that the smaller blocks (8) of the prefabricated block (10) form a brick pattern.

9. 9. The vehicle arresting system of claim 8, wherein the one or the second plurality of smaller blocks (7, 8) of the upper layer (9) of the layered prefabricated block (10) has a first compressive strength, the one or the second plurality of smaller blocks (7, 8) of a first layered layer (9) below the upper layer has a second compressive strength, and the one or the second plurality of smaller blocks (7, 8) of a second layered layer (9) below the upper layer has a third compressive strength, and so on down to the lower layered layer (9), where the first compressive strength<the second compressive strength<the third compressive strength, and so on down to the lower layered layer (9).

10. 10. The vehicle arresting system of claim 9, wherein the layered layers (9) of the prefabricated block (10) are inclined such that the layered layers (9) are substantially parallel to a longitudinal central axis of the longitudinal direction and incline laterally downward toward the longitudinal central axis of the arrester bed.

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